1. Field of the Invention
This invention relates to disc-type valves as used, inter alia, in industry to control the flow of gaseous and fluid materials in pipelines.
2. Description of the Prior Art
In the known disc-type valves, the sequence of opening and closing of the valve is accomplished entirely by means of various arrangements of levers, both with and without some means of guiding the motion of the valve disc in relation to the valve seat. Disc type valves utilizing a guide means in addition to a lever action provide a means of positive control of the motion of the valve disc at all points in its travel, whereas designs using merely the lever principle only generally direct the opening and closing of such a valve without benefit of precise control. The guide means used in known valves of this type incorporate various designs which only add additional lever actions. For the longitudinal movements of the valve disc, control by such lever actions is satisfactory. Problems develop at the point where the disc must be pivoted to insure minimal restriction to material flow through the valve. Specifically, the problems develop where these types of valves are used in applications wherein there is a significant degree of operational temperature variation. Due to different degrees of expansion and contraction of the masses of material of the component elements, the geometry of articulation changes. The result is a tendency for the lever actions, at certain temperatures, to bind at the point where the disc is to be pivoted. There is a need to provide a means by which such binding can be overcome, thus insuring a positive pivotation of the valve disc through the range of operating temperatures of the valve.
In the known disc type valves, there is reliance, to some degree, on the force of gravity to articulate the valve disc. Therefore, these valves cannot be operated in positions other than that for which they are designed. There is a need for a standard articulation mechanism for disc type valves used at elevated temperatures which does not depend on gravity but can be used equally as well in any position. Such a standard articulation mechanism would reduce the cost of manufacturing valves of this type by reducing the number of different designs required to produce valves for all of the possible variations in position in which such valves are used.